1. Field of the Invention
The invention relates to processes for using electrophotographic systems to make and assemble a number of color toned images to provide a full color reproduction.
2. Background of the Art
Full color reproductions generated by electrophotography were disclosed by C. F. Carlson in his early patents (U.S. Pat. No. 2,297,691) but no detailed mechanisms were described. Another early patent (U.S. Pat. No. 2,752,833) discloses a method based on a single transparent drum coated with a photoconductor around which a web of receptor paper is fed. Electrostatic images are produced on the drum and by induction on the receptor paper. The electrostatic image is generated by line scan exposure from inside the drum. Full color images are provided by a cathode ray tube (CRT) which uses three separate scan lines representing different colors. The three lines are directed optically to three different points on the drum. Charging stations precede and toner stations follow each of these scan positions. Time delays between the scans ensure registration of the different color images. The final tricolor image is assembled directly on the receptor paper. In U.S. Pat. No. 4,033,688 (Agfa-Gevaert) a single photoconductive drum is exposed to three different color beams reflected from a color original, at points around its circumference. Each point being provided with the requisite charging and toning stations. Mechanical time delays ensure registration of the three color images which are then transferred to a receptor sheet. Other similar systems are disclosed in U.S. Pat. Nos. 4,403,848 and 4,467,334.
Other single photoconductor drum systems (e.g., U.S Pat. Nos. 4,234,250; 4,236,809 and 4,336,994) create the individual color images on the drum and transfer them to a receptor one at a time. A number of other patents in color proofing use this procedure, following it with a flat platen. Exposure is by laser scan (U.S. Pat. Nos. 4,286,031; 4,358,195; 4,547,061 and 4,556,309).
Many patents e.g., U.S. Pat. Nos. 2,986,466; 3,690,756 and 4,370,047) use three or four different photoconductor drums or belts for the different colors and assemble the individually toned images in register on a receptor sheet.
Exposure by conventional optical scanning is disclosed in many patents e.g., U.S. Pat. Nos. 3,690,756; 4,033,688; 4,234,250. CRT scanning is disclosed in U.S. Pat. No. 2,752,833, and laser scanning on its own or in combination with conventional exposures occurs in patents such as U.S. Pat. Nos. 4,234,250; 4,236,809; 4,336,994; 4,348,100; 4,370,047; 4,403,848 and 4,467,334.
Color proofing systems based on electrophotography are disclosed, for example, in U.S. Pat. Nos. 4,600,669 and 4,358,195, the latter having been mentioned above.
U.S. Pat. No. 4,403,848 describes a multicolor, photoconductor imaging apparatus and process. Radiation is imagewise scanned over a photoconductor surface for each color toner to be applied. Imagewise discharge of the photoconductor is performed while previously toned color images are present on the photoconductor. This is accomplished by using toners which have a window for the imaging radiation or are transparent to the imaging radiation. Photoconductive imaging is effected by splitting the imaging beam and directing the various portions of the beam to different points along the movement path of the photoconductor. After association of the various color images on the photoconductor, the associated multicolor image is transferred to a receptor surface.